The present invention relates to a fuel injection valve of a direct injection engine.
For example, EP2302197A1 (JP2010-019194A) discloses a solenoid-operated fuel injection valve. The fuel injection valve opens outwardly, and includes a cylindrical case partitioning a fuel passage within a valve body, and a movable core provided to be movable inside the case in a cylinder axial direction and for stroking a valve body for opening and closing a nozzle hole. The fuel injection valve also includes a solenoid coil arranged on the outside of the case and for attracting the movable core by forming a magnetic circuit over the inside and outside of the case during a power supply to the solenoid coil, so that the valve body opens the nozzle hole.
Since the fuel injection valve disclosed in EP2302197A1 (JP2010-019194A) directly injects fuel inside a cylinder of an engine, fuel pressure is set comparatively high. Since the case partitioning the fuel passage receives an internal pressure corresponding to the fuel pressure, sufficient strength for withstanding the internal pressure is required for the case. Accordingly, the strength required for the case increases as the set fuel pressure is higher.
In a solenoid-operated fuel injection valve, the case constitutes a part of the magnetic circuit. Therefore, the case is constituted by a material with high magnetic permeability and low residual magnetism, such as ferritic metal. However, ferritic metal is inconvenient in terms of strength. Therefore, when the fuel pressure is set high, the case needs to be thickened significantly so as to satisfy the required strength. However, if the case is thickened too much, then the magnetic circuit formed over the inside and outside of the case cannot be formed. Thus, the solenoid-operated fuel injection valve has a problem that it is difficult to increase the fuel pressure.
The present invention is made in view of the above situations and provides a solenoid-operated fuel injection valve in which setting of high fuel pressure is available.